DO NOW: (5 MIN)

New Unit: Motion

1. A car travels at 64 mph. How far would it travel in 3.5 hours?2. What are the units you would use to describe the speed of a car? The speed of a bike? The speed of a person? The speed of light?

New Unit:

Motion!

Categorizing measurements and quantities

Scalar: quantities fully described by a magnitude (or numerical value) alone Examples: 60 mph, 100 degrees Celsius,

250 MegaBytes

Vector: quantities only fully described by both a magnitude and a direction Examples: 20 m/s North, 36 pounds 50

degrees North of East, 6 miles South

Practice!

Categorize each of the following quantities as scalar or vector

5 m 30 m/s East 20 degrees Celsius 90 lbs 32 degrees West of South 256 bytes 4000 calories 5 mi North

Distance vs. Displacement

Distance(scalar): "how much ground an object has covered" during its motion.

Displacement (vector quantity): an object's overall change in position, starting from its reference point

http://physics.info/displacement/ http://www.splung.com/content/sid/2/

page/distance

Example #1 Consider the motion depicted in the

diagram below. Ray Lewis walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North… then knocks someone’s helmet off

Example #1

What is his distance (how far he walked)?

What is his displacement (how far away he is from where he started)?

*Reminder: Vector quantities such as displacement are direction aware. Scalar quantities such as distance are ignorant of direction.

Example #2

Use the diagram to determine the resulting displacement and the distance traveled by the skier during these three minutes. Minute 1

Minute 2 Minut

e 3

Example #2

To find the distance, add up the lengths of the arrows:

To find the displacement, measure how far the skier is from where he started:

Minute 1

Minute 2 Minut

e 3

Distance:180+140+100 = 420mDisplacement

: from A to D is 140 m

*Displacement*

Example #3

A football coach paces back and forth along the sidelines. The diagram below shows several of coach's positions at various times. At each marked position, the coach makes a "U-turn" and moves in the opposite direction; the coach moves from position A to B to C to D.

Example #3

What is the coach's resulting displacement

and distance of travel?

55m

35+20+40=95m

More Practice

1. What is the distance and displacement of the cross-country team if they begin at the school, run 10 miles and finish back at the school?

2. What is the distance and the displacement of the race car drivers in the Indy 500?

Speed and Velocity

Speed(scalar): "how fast an object is moving.“

Velocity (vector):"the rate at which an object changes its position."

Calculating Average Speed and Average Velocity

Next week we will calculate instantaneous as well as average speed and velocity!

Rate of Change

Rate of change: the speed at which a variable changes over a specific period of time; is often illustrated by the Greek letter delta ∆

Both speed and velocity are rates of change. Speed is the change of distance over time Velocity is the change of displacement over

time We can find the rate of change for any

variable that changes over time – we will investigate this tomorrow in a mini-lab!

Practice

Please use the remainder of class to work on your worksheet. It is due Friday, September 24.

In uno stesso moto equabile, lo spazio percorso in un tempo più lungo è maggiore dello spazio percorso in un tempo più breve.

Do Now (9/23):A child walks 1.5 miles to school, 1.5 miles home, then 1.5 miles back. It takes him 1.25 hours total.

1. What is his distance?2. What is his displacement?3. What is his speed?4. What is his velocity?